Air separator



AIR SEPARATOR Filed 001'.. 25, 1938 3 Sheets-Sheet 1 I. 5| :I i: 35 i 35 ii a /5 1 e 8 I iras 1 v$5 8 a1 y mi' il l e? 'E l F' a v a4 c1 1 24 l 13 1.-: 1.9 2.5 s 65 4 66 a5 fa P1 4 4 P1 P3 l f 69 '1\ 3 so a? 8 v f1 INVENTOR 1? BY l 'WATTORNEY Jan 30, 1940- T. J sTURTEvAN-r 2,188,634

AIR SEPARATOR Filed Oct. 25, 1938 3 Sheets-Sheet 2 INVENTOR 77m., Tamm ATTORNE Jan. 30, 1940. T. .L sTUR'rEvAN'r 4 AIR SEPARATOR Filed Oct. 25, 1958 3 Sheets-Sheet 5 INVENTR BY ATTORNE Patented Jan. 30, 1940 STATES lilt SEFRATR AThomas J. Sturtevant, Wellesley, Masspassgnor.

to Sturtevant Mill lflonipany,v Boston, Mass.,'a corporation of Massachusetts Application October 25, 1938, Serial No. 236,355

13 Claims.

My invention relates to air separators of the whirlwind type for grading and separating material. The general principles and performance of such air separators are illustrated and described in a number of my prior patents. The object of this invention is to improve prior air separators in such manner as to give a maximum control of the size of the finished product while the separator is in operation.

The nature of my invention and its features for achieving the above object will best be understood from the following detailed description of the preferred form of the invention as at present known to me and illustrated in the accompanying drawings, the scope of the invention being indicated inl the appended claims. In the drawings:

Figure 1 is a, view,v in vertical section and diagrammatical in part, through a separator of the whirlwind type illustrating the novel features of this invention;

Fig. 2 is a view, in plan, of the head of a separator having certain controls according to this invention;

Fig. 3 is a view, in sectional plan, of a quadrant of the separator looking down on the rejector fan and on the sliding plate valve above said fan, as indicated by the line 3 3 on Fig. 1;

Fig. 4 is a view, in sectional plan, through the supports for and just above the double distributor plate', as indicated by the line 4 4 on Fig. 1; and

Figs. 5 and 6 both illustrate a single rejector fan vane each of a modified form from that shown in Fig. 1 while yet preserving the function of the baille plate above the distributor.

Fig. l of the drawings is illustrative of the type of air separator in which the present invention preferably is embodied and comprises an outer cylindrical casing I supporting a spaced inner casing 3 set downward from a flat head cover 5 on the casing I providing a main or circulating fan chamber l above'the casingl 3. The outer casing I has a cone 9 at its lower end terminating in a fines discharge spout II. The inner casing 3 is somewhat contracted at its lower portion and supports a circular series of generally tangentially set inlet vanes I3. Below the vanes I3 the cone 9 supports a spaced inner cone I5 having a tailings discharge spout I'I extending laterally through the wall of the cone 9.

The inner casing 3 is substantially uncovered having, for the most eflicient performance of a separator providing the present improvements, merely a. narrow marginal shelf I9 which extends partially into the collecting chamber 2l formed by the spaced relation of the casings I and 3. The space within the inner casing 3 constitutes a separating chamber 23 and its ring-plate cover I9 is so dimensioned that it affords a top opening 24 communicating with the main fan chamber l having a maximum area of 80% to 90% of the area of the separating chamber at this level. As illustrated in Fig. 1, the rejector fan, within the separating chamber and having its vanes 25 10 above and beyond a circular baille plate 26, has the same or only a slightly smaller diameter than that of the top opening 24 for its maximum rejective power. The marginal shelf I9 functions also to support an adjustable plate-valve com- 15 prised of a circular series of alternating overlapped plates 2l each of which may individually be slid inward and outward by means of an attached adjusting rod 29 extending radially outward through a suitable stuiiing-box guide on the casing wall. When the plate-valve is fully open the circle formed by the inner edges of its plates 2l will be coincident with or outside of the inner perimetral edge i90. of the shelf I9 (see Fig. l). By manipulation from outside the separator the 25 plates 2l may be slid inward by their control rods 29 to a greater or less degree over the rejector fan vanes 25, simultaneously reducing the size of the top opening 24 (see Fig. 3).

It will be observed that on rotating the main 30 fan its vanes 8 will draw the air upward through the rejector fan and through the separating chamber top opening 24 and throw it outward to the collecting chamber wherefrom it is sucked inward in a swirling motion and re-enters the lower part of the separating chamber through the circular vane-valve I3 whirling then up- Ward outwardly to pass the baiile 26 and so again to the main fan. Thus the air circulates continuously in a closed circuit. The unclassified material fed into the air current must, as it is carried upward, pass through the rejector fan vanes 25 and be subjected to the classifying action thereof before its fines can pass over into the collecting chamber 2I'and then downward 45 to the fines discharge spout AI I. 'Ihe heavier tailings,A batted outward by the rejector fan vanes, drop downward at the outer margin of the separating chamber and thus to the tailings discharge spout I1.

The material to be classified is delivered centrally to a two-part rotary distributor within the separating chamber, indicated generally by 30 in Fig. 1, and located below the baule 26. The motion of the distributor throws the material outward by centrifugal action where it is then caught and carried upward into the classifying zone by the rising air current. A cone 3| extends downward through the top opening 24 of the separating chamber from the cover of the casing I and occupies a position centrally above the distributor 30. I'his cone 3| serves as a feed hopper and may be supplied from outside the separator through a feed chute communicating with the cone 3| and having feed opening 33 (Fig. 2) through the cover 5 substantially as disclosed in my prior Patent No. 2,030,612 of February l1, 1936.

The casing cover 5 carries a pair of channel bars 35 (Fig. 2) which support a base casting 31 carrying a shaft housing 39 extending downward centrally within the feed hopper 3|. This housing has a set of bearings 4| at its lower end for a hollow driving shaft 43 which extends upward from the distributor 30, through an under gear box 44 carried by the base plate 31 where it has a set of upper bearings 45. Within the hollow shaft 43 is a solid driving shaft 46 which is stepped in a bearing 41 carried by the hollow shaft 43 below its lower extremity. The solid shaft 46 extendsupward to an upper gear box 48 where it has a set of upper bearings 49. Within the under gear box 44 a bevel gear l50 on the hollow shaft 43 meshes with a bevel pinion 5| on a suitably supported short, horizontal power shaft 52. Similiarly within the upper gear box 48 a bevel gear 53 on the solid shaft 46 meshes with a Ibevel pinion 54 on a suitably supported short, horizontal power shaft 55. The two power shafts 55 and 52 conveniently extend in opposite directions from the upper and under gear housings thus giving roomI for mounting two motors (not shown) on the casing cover 5, one or both being of the variable speed type, for independent and selective rotation of said shafts through suitable transmission devices, for example a pulley on each shaft belted to its respective motor.

As stated, the foot of the hollow shaft 43 is above the foot of the solid shaft 46. The foot of the hollow shaft 43 supports a casting having a sleeve 51 (Figs. 1 and 4) fast on the shaft and presenting below the sleeve a smooth faced circular plate 59 which forms the inner part of the two-part distributor 30. Rising from a ring that is bolted to a peripheral ledge on the inner distrlbutor plate 59 is a circular series of posts 60 supporting a generally cone-shaped rotary sleeve 6| shaped to surround the lower part of the feed hopper 3|. The space between this sleeve and the xed feed hopper may be closed by a form of piston ring seal as indicated on Fig. l. At the upper end of the sleeve a flange 63 extends outward within the main fan chamber 1. This flange supports a series of fan arms 65 on which the vanes 6 of the circulating fan are mounted for radial adjustment. The sleeve 6| also has an outwardly extendingr lower flange 66 to which the segmental plates (Fig. 3) forming the large baille 26 are bolted. Thus, rotation of the hollow driven shaft 43 will rotate the baiiie 26 with the circulating fan vanes 8.

The foot of the solid driving shaft 46 supports a rotary spider 61 the legs of which carry a ring at their upper ends presenting a smooth faced annular plate 69 which forms the outer part of y cular series of posts supporting a ring-plate 1| that is located just below the baille 26. 'Ihe ring-plate 1| presents a ange or annular hub to the underside of which there is bolted a. series of radial arms 13 each supporting, at its outer end, a rejector fan vane 25. Thus, rotation of the solid driving shaft 46 will rotate the rejector fan independently of the rotation of the circulating fan. It has been found to be sucient, ordinarily, to provide a reversible motor only for the solid or rejector fan shaft.

The annular or ring distributor 69 is. of necessity, of considerable diameter which makes the addition of a plate extension, for example as shown in Fig. 1 of my said U. S. Patent No. 2,030,612, unnecessary, although for special work i such a plate extension might be used to advantage. i

'I'he baille 26 is of such a. diameter as to extend from its central support substantially to (Fig. 5) or even beyond (Fig. l6) the inner vertical edge of the average size of rejector fan vane 25a thereby completely batlling the area within the inner edges of the vanes and preventing the material from passing upward other than through the selective zone controlled by the rejector fan. The preferred construction is shown in Fig. 1 where the inner edge portions of rejector fan` vanes 25 are notched, the marginal portions of the baille engaging within these notches. If desired, a corner cut-out as shown by the vane 25h (Fig. 6) may be employed to permit retention in the assembly of the large baille. I

A removable trap (Fig. 2) is provided in the casing cover 5 permitting a workman to enter the separator when necessary.

'I'he object of this invention, i. e., a maximum control of the finished particle size while the separator is in operation may be attainedto a varying extent by several methods of control used alone or in combination. One method is by an adjustment of the sliding plate valve by which the size of the top opening from the separating chamber and the effective area of the rejector fan vanes is changed by the varying overlapping eflect of the valve plates (see Fig. 3). Another method is changing the relative speeds of the main or circulating fan located outside the separating chamber and of the rejector fan located inside theseparating chamber. Both of these methods of control, practiced at will from outside the separator, are embraced bylthis invention.

The separating chamber of the air separator of this invention is, preferably, provided with a top opening of a diameter substantially equal to the diameter of the rejector fan which sweeps just beneath it. Ihe vane arms of the rejector fan are so long as to locate its vanes well out in the classifying zone and below the outer margin of said oversize top opening. Combined with such a rejector fan is the large interior baille. With this construction practically all the material laden, upward current of air induced by the main fan has to pass between the vanes of the rejector fan where the undesired or oversized particles are centrifugally whirled and batted out of the air stream toward the wall of the separating chamber and thus caused to drop :soA

down and only the desired fines are permitted to be drawn through into the main fan chamber and thence to the collecting chamber.

'I'he power of the rejector fan"K to prevent undesired or oversized product of the classification to pass upward will depend on two factors, speed of rotation and the number oi vanes. In order to provide for a maximum control of the product while the separator remains in operation, such number of vanes would be used as is adapted to the average work to be done by the separator when the speed of rotation of the rejector fan is the same as that of the main fan and control of the product secured by changing the speed of rotation of the rejector fan relatively to that of the main fan.

The rejective power of the rejector fan for a given number of vanes will vary with its speed of rotation, for a finer product faster and for a coarser product slower, the speed of rotation of the main fan being unchanged. This is because the centrifugal and batting action of the rejector fan increases very rapidly with its speed of rotation. Increasing its speed causes it to selectively reject a larger and larger proportion of the material carried upward by the circulating air stream. Accordingly, as the speed of rotation of the rejector fan, is increased relatively to'that of the main fan a finer and finer product passes through it and over into the collecting chamber.

Furthermore, the rejector fan opposes the main fan more or less and, therefore, a change in its speed of rotation tends to control or vary the upward velocity of the rising air current in the separating chamber, which velocity controls the maximum size of particle that can be lifted by the air stream.

The opposing power of the rejector fan to the main fan depends, for any fixed number of vanes, to a large degree on the size of the top opening from the separating chamber as compared to the diameter of the rejector fan, or, in other words on the amount of the overlapping of the sliding valve plates, in an inward direction, over the closely adjacent vanes of the rejector fan. Herein these valve plates have a range of from no overlap of said vanes at the largest diameter of the top opening to a large overlap of said vanes at its smallest diameter. This device, when combined with the means for varying the speed of rotation of the rejector fan, gives a maximum control of the air current in a closed circuit and is eifective to control the particle size recovered as fines throughout a Wide classification range. For example, with cement as the material being classified this separator is eifective without stopping its operation throughout a practical classification range of 1500 to 3000 surface area of particle size.

Those skilled in the art will recognize that an air separator` having the features herein described is capable of adjustment in various ways to attain maximum control of the finished product during continuance of its operation.

In the accompanying drawings the relative position of some of the adjacent parts is exaggerated in order to present with clarity the preferred constructions, the principle involved and consequent scope of the invention being made clear by the description and the appended claims.

It is to be understood that'the phraseology or terminology employed herein is for the purpose of description and not of limitation and it is not intended to limit the invention beyond the terms of the several claims hereto appended as consdered in view of the prior art and the requirements thereof.

What is claimed as new, is:

l. In an air separator of the type described having a central separating chamber through which the air current is drawn upwardly from an adjacent collecting chamber by a rotary main fan in a fan chamber above the separating chamber, a rotary distributor supported centrally within the separating chamber for discharging material to be graded, a top opening for the separating chamber through which the material laden air passes to the fan chamber, a rotary rejector fan in the separating chamber the vanes of which sweep just below the outer zone of said top opening and are provided with notches at their inner edge portions, a rotary baffle plate, whose marginal portion engages within the notches of said varis and which is arranged above said distributor, baiing the area within said rejector fan vanes and forcing substantially all said material laden air to pass through the rejector fan, said bale plate being rotatable independently of said rejector fan but simultaneously with said main fan, means operable while the separator continues in operation for varying the rejective power of said rejector fan comprising a device for varying the diameter of said top opening, and mechanism for varying the speed of rotation of said rejector fan independently of said main fan and said baffle plate.

2. In an air separator of the type described, a separating chamber having a top opening and a bottom opening, means for creating air currents and for circulating said air currents upward through the separating chamber in a closed circuit, an outer hollow driving shaft extending downwardly from above the separator centrally within the separating chamber, an inner driving shaft within said hollow shaft, bearing and driving means providing for independent rotation of said two shafts at selective speeds at the will of the operator, a two part rotary distributor at the lower ends of said shafts for discharging material to be graded into said rising air currents, one part comprising a rotary sleeve and being connected to and rotating with one shaft and the other part being connected to and rotating with the other shaft, a feed hopper for ungraded material surrounding said outer shaft and, together with said outer shaft, defining an annular feeding channel leading downwardly from outside the separator to said distributor, said rotary sleeve encompassing the lower portion of said hopper and being spaced therefrom, and a sealing ring fitted into and closing the space between said rotary sleeve and the lower portion of said hopper.

3. The invention as described by claim 2 in which said distributor comprises inner and outer parts, said inner part comprising said rotary sleeve and being connected to said outer shaft and said outer part being connected to said inner shaft.

4. The invention as described by claim 2 in which said distributor comprises a circular plate and an annulus encircling said circular plate.

5. The invention as described by claim 2 in which said distributor comprises a circular inner plate mounted on said outer shaft and an annular outer plate mounted on said inner shaft.

6. In a separator of the type described, a separating chamber having a top opening and a bottom opening, a central hollow driving shaft extending from above downwardly to within the separating chamber, a solid shaft within said hollow shaft extending both above and below said hollow shaft, bearing and driving means providing independent rotation of said two shafts, a circulating fan in a fan chamber above said top opening carried and driven by said hollow shaft for drawing air currents upward through the separating chamber, a rejector fan within the separating chamber below said top opening carried and driven by said solid shaft, a rotary distributor supported at the lower ends of said shafts, said distributor comprising a rotary sleeve, a feed hopper for ungraded material surrounding said hollow shaft and, together with said hollow shaft, defining an annular feeding channel leading downwardly from outside the separator to said distributor, said rotary sleeve encompassing the lower portion of said hopper and being spaced therefrom, and a sealing ring fitted into and closing the space between said rotary sleeve and the lower portion of said hopper.

'7. The invention as described by claim 6 in which said distributor is formed of two parts, viz., a central plate carried and rotated by the hollow shaft and an encircling annular plate carried and rotated by the solid shaft, said annular plate comprising means for supporting said rejector fan and said central plate comprising said sleeve and means for supporting said circulating fan.

8. The invention as described by claim 6 in which said distributor is formed of two parts, viz., a central plate carried and rotated by the hollow shaft and an encircling annular plate carried and rotated by the solid shaft, said annular plate comprising means for supporting said rejector fan and said central plate comprising said sleeve and means for supporting said circulating fan, and a rotary baille located within the separating chamber in a position to direct substantially all the material laden air currents through the rejector fan and supported by the means for supporting said circulating fan.

9. In a separator of the type described, a separating chamber having a top opening and a bottom opening, an outer hollow driving shaft eX- tending from above downwardly to within the separating chamber, an inner driving shaft Within said hollow shaft, bearing and driving means providing for independent rotation of said two shafts at selective speeds at the will of the operator, a circulating fan in a fan chamber above said. top opening for drawing air currents upwardly through the separating chamber, a rejector fan within the separating chamber below said top opening, a two-part rotary distributor at the lower ends of said shafts for discharging material to be graded into said rising air currents, one part comprising a rotary sleeve and being connected to and rotating with said outer shaft and the other part being connected to and rotating with said inner shaft, said one part carrying said circulating fan and a rotary baffle plate forcing substantially all said rising air currents to pass through the rejector fan and said other part carrying said rejector fan, a feed hopper for ungraded material surrounding said outer shaft and, together with said outer shaft, defining an annular feeding channel leading downwardly from outside the separator to said distributor, said said hopper and being spaced therefrom, and a sealing ring fitted into and closing the space between said rotary sleeve and the lower portion of said hopper.

10. In an air separator of the type described having a rotary main fan for circulating a whirling current of air in a closed circuit upwardly through the top opening of a separating chamber and downwardly through a collecting chamber including a rotary rejector fan equipped with vanes and arranged in the separating chamber closely adjacent said top opening to describe an annular zone of rejecting action, a rotary baille plate winch is arranged within said separating chamber and Whose marginal portion cooperates with the inner edge portions of said vanes to close off substantially completely the area within said annular zone and to direct substantially all the air in said circuit upwardly through said annular zone of rejecting action described by said rejector fan vanes, said baffle plate being rotatable independently of said rejector fan but simultaneously with said main fan, and means eiective throughout a wide classification range of the particle size recovered as fines and operable from outside the separator during its continued operation, for regulating the power of said rejector fan to prevent undesired product of classification from passing upwardly.

1l. The invention as defined by claim 10 in which said mea'ns comprises a device for varying the diameter of said top opening relative to the diameter of the rejector fan in combination with mechanism operating upon the rejector fan for varying the upward velocity of the rising air current within the separating chamber.

12. The invention as defined by claim 10 in which said means comprises a sliding valve plate above the rejector fan and above said top open# ing operable to decrease the effective diameter of said top opening and simultaneously to overlap the vanes of the rejector fan thereby to increase its rejective power and mechanism for varying the speed 'of rotation of the rejector fan relative to that of the main fan.

13. In an air separator of the type described, a separating chamber having a circular top opening of from about to about 90% of the area of the separating chamber at its top, a rotary rejector fan having a `diameter approximately equal to but not greater than the diameter of said top opening, said fan being equipped with vanes whose upper edges sweep substantially in the plane of said top opening and whose inner edge portions are provided with notches, a rotary circulating fan above said top opening, a rotary baille plate whose marginal portion engages within the notches of said rejector fan vanes and which is arranged to force substantially all material laden air to pass through said rejector fan, said baille plate being rotatable independently of said rejector fan but simultaneously with said circulating fan, and means for rotating the circulating fan and the rejector fan at selective speeds independently of each other.

THOMAS J. STURTEVANT. 

